1. Field of the Invention
The present invention relates generally to a method and an apparatus for treating poor laryngeal-elevation disorder with sequential-high voltage electrical stimulation.
2. Description of the Prior Art
The mechanism of normal human swallowing involves 3 phases:
Phase 1: is the oral phase, during which food in the oral cavity is masticated and mixed.
Phase 2: is the pharyngeal phase, during which the masticated and mixed food bolus is propelled from the oral cavity into the pharyngeal lumen and thence into the upper oesophagus. The second phase of swallowing involves the use of the glossal muscles and the pharyngeal muscles (suprahyoid and thyrohyoid) and a lowering of the base of the tongue. The tongue muscles then propel food bolus from the oral cavity into the pharyngeal lumen. At this stage, the muscles of the pharynx contract in sequence, raising elevating the larynx and moving it forward in order to open the pharyngeal lumen and the upper oesophageal sphincter so that the bolus can pass readily into the upper oesophagus.
Phase 3: is the oesophageal phase and marks the phase of peristaltic propulsion of the bolus through the oesophagus and into the stomach.
There are many different treatment modalities for dysphagic patients depending on the pathology of the patient. For instance, in patients who have difficulty with the initiation of swallowing, the swallowing reflex may be stimulated by a special device (U.S. Pat. No. 5,891,185) or by the use of a cooled dental mirror to stroke the anterior tonsillar pillar.
For patients in whom the function of the pharyngeal muscles is absent, reduced or uncoordinated, laryngeal elevation may be insufficient or absent. This has the effect of reducing the width of the pharyngeal lumen and an inadequate opening of the upper oesophageal sphincter. The patient therefore experiences difficulty in swallowing or may aspirate food into the larynx and the trachea. Such patients may be treated with several methods such as, for instance, exercise of the pharyngeal muscles using various biofeedback devices which enhance contraction of the pharyngeal muscles, or surgery to retract the larynx to the mandible, to close the larynx, or to resect the upper oesophageal sphincter. None of these treatments offers an automatic and dynamic cure, i.e., a means to increase the function of the pharyngeal muscles and aid in the elevation of the larynx actually during the swallow.
Treatment of patients with dysphagia associated with dysfunction of the pharyngeal muscles using previously available high voltage stimulators, which are non-automatic and which are applied during regular sessions, is able to increase the power of contraction of the pharyngeal muscles and suprahyoid and reduce the symptoms of patients with mild dysphagia, but is ineffective for severely dysphagic patients or those who aspirate when swallowing.
During development of the sequential stimulator for treatment of dysphagic patients emphasis was placed on the need to provide physiological stimulation of the muscles of deglutition, i.e, providing stimulation only at the time that the patient attempts to make an actual swallow, instead of during regular sessions of physical therapy. The device, therefore, is neither intended nor capable of initiating swallowing. Instead it has the capability to detect when the patient makes an attempt to swallow and responds by sending a sequence of high voltage stimuli to the muscles of the suprahyoid and the thyrohyoid muscles, whose contraction elevates the larynx and opens the pharyngeal lumen in order to allow the food bolus to pass through the pharynx. The device thus reinforces the normal process during swallowing, and is of particular value for the treatment of dysphagia due to the central nervous system lesions, or where immediate restoration is needed, for instance, in cerebrovascular accident, muscle weakness due to aging, and disruption of normal motor pathways.
The purpose of this invention is to provide sequential electrical stimulation for the treatment of dysphagic patients. The invention comprises 2 functional entities. The first functional entity of the device is responsible for monitoring the electrical signal from the glossal muscle picked up using skin surface electrodes placed bilaterally in the area of the patient""s submandibular salivary glands or from the temporalis muscle picked up using skin surface electrodes placed bilaterally in the patient""s temporal region. The surface electromyographic signal is then passed to a circuit responsible for detecting an attempted swallowing event. When an attempted swallowing event is detected, a trigger signal is sent to the second functional entity of the device, which is responsible for generating a high voltage pulsed stimulus which is delivered to the suprahyoid or masseter muscles and the thyrohyoid muscle. Contraction of these muscles in response to stimulation has the effect of elevating the larynx and when this occurs the pharyngeal lumen is widened, thereby allowing the easy passage of the food bolus through the pharynx into the upper oesophagus. Thus the sequential stimulator for treatment of dysphagic patients assists the normal physiological mechanism of swallowing, and does so at the moment when the patient attempts to perform a swallow.
The sequential stimulator for the treatment of dysphagic patients comprises a unit which is capable of detecting a swallowing signal from the glossal or temporalis surface electromyograph (SEMG). When a swallowing signal is recognized, a trigger signal is sent to the stimulation generation unit to release high voltage stimuli sequentially to the suprahyoid muscles or the masseter muscles and the pharyngeal muscles in order to assist in the elevation of the larynx. This enables the pharyngeal lumen to open more widely so that food can pass through the patient""s pharynx and into the oesophagus more easily during swallowing. Thus the sequential stimulator is a device for assisting swallowing in patients with dysphagia due to a variety of causes, for instance, brain injury, cerebrovascular accident, injury of the cervical nerves, muscles weakness, or old age. The stimulator is operative only when the patient attempts to swallow and provides a physiologic stimulus and provides a means of immediate relief of the swallowing difficulty. However, the device is also useful for physical therapy whereby the muscles under the chin, the masseter muscles and the pharyngeal muscles can be re-educated to contract in the normal coordinated sequence.